The program also uses observed station azimuths as given in the Nordic Format. Station azimuths can be obtained with either 3-component stations or array stations or by using a local network as an array (see EEV pfit option) This means that the program can locate with one station if it has at least two phases like P, S and azimuth. Azimuth residuals contribute to the overall rms, see TEST(52) and section on weight. In order to locate with one station, azimuth and P and S, TEST(56) MUST be set to 1. Note that the depth then will be fixed to the starting depth. So if the starting depth is larger than the hypocentral distance, no solution is possible and the starting depth must be set to a value smaller then the hypocentral distance. This can be done in the STATION0.HYP file or individually in the S-file. Known problem: If Azimuth on one station and P and S on another station, HYP might not locate properly.
NOTE: XNEAR must be larger than the distance to the station. If TEST(58) is set to a value lower than the apparent velocity associated with the backazimuth, no location will be made.
Peter Voss : Tue Jun 8 13:38:42 UTC 2021